JPH05165261A - Color liquid developer for electrostatic photograph - Google Patents

Abstract

PURPOSE:To improve color reproducibility and to avoid color overlap fogging by using a compd. comprising an oil-base aliphatic hydrocarbon with dispersion of a specified nonwater resin. CONSTITUTION:This electrostatic photographic color liquid developer consists of a toner essentially comprising a pigment and resin dispersed in a carrier. The resin is a nonwater-base resin obtd. by polymn. of monomers expressed by formula with styrene-butadiene copolymers and/or vinyltoluene-butadiene copolymers, and is dispersed in an oil-base aliphatic hydrocarbon. Or, the resin is a nonwater base resin obtd. by polymn. of monomers expressed by formula and monomers which become insoluble with an oil-base aliphatic hydrocarbon solvent when homopolymerization is effected in this solvent. In formula, R is H or CH3, X is -COOCnH2n+1 or -OCOCnH2n+1, and (n) in the substituent is an integer 6-20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic latent image formed on an electrophotographic photosensitive member or an electrostatic recording member by electrostatically adhering toner particles onto the electrostatic latent image so as to form a visible image and superimpose colors. The present invention relates to a color liquid developer for photography.

[0002]

2. Description of the Related Art In order to obtain a full-color image by electrophotography or electrostatic recording, an electrostatic latent image is formed on an electrophotographic photosensitive member or electrostatic recording paper by a conventional method, and a primary color in accordance with the destructive color mixing method is used. It is obtained by electrostatically adhering toner particles in a liquid developer, visualizing them, and superposing colors.

The liquid developer used in this method contains cyan, magenta, and yellow pigments as well as rosin, linseed oil, soybean oil, modified alkyd resin, styrene-butadiene resin, acrylic resin, and other resins or fats and oils. It is obtained by pulverizing and dispersing in a carrier liquid having a high insulating property and a low dielectric constant such as hydrocarbon.

In the color electrostatic photography, it is desired that the liquid developer has various properties in order to superimpose the toners of the respective primary colors as described above, but particularly good color reproduction can be obtained. is necessary.

However, when the formation and development of the electrostatic latent image are repeated in the order of black, cyan, magenta and yellow using the liquid developer obtained by the above-mentioned method, the previously developed portion remains. Due to the development of the toner in the next step with respect to the electric potential, extra toner adheres, which causes a problem of poor color reproducibility. This development is referred to herein as color overlap fog due to residual potential.

It is known that the reduction of the residual potential can be achieved by adding a charge removing mechanism such as light, heat and ion irradiation to the device. As an example, when a photoconductive monomer is introduced into the resin constituting the toner and a process of irradiating light after development is added, the residual potential after development with the toner is rapidly eliminated by irradiation with light, Next, when another latent image is formed and developed with another toner, an excessive color overlapping fog does not occur in the portion where the latent image is not provided. However, such a method is not an advantageous method because the structure of the device is complicated and the cost is increased.

Therefore, in order to improve the color overlapping fog due to the residual potential in the characteristics of the developer, there are two ways of thinking in addition to the above photoconductive toner. One is a method of sufficiently neutralizing an electrostatic latent image with toner particles, and the other is a method of leaking electric charges into a carrier liquid constituting a liquid developer.

When these methods are carried out singly or in combination, there is almost no color overlapping fog in the initial quality, but when toner is consumed by copying, color overlapping fog occurs or in the liquid during the copying process. It is difficult to say that an image with good color reproducibility can be stably obtained, because there are drawbacks such that the image density decreases quickly because the ion concentration of It was a thing.

To solve this problem, Japanese Patent Application No. 2-25
No. 6576 proposes a non-aqueous resin obtained by polymerizing a styrene-butadiene copolymer or a vinyltoluene-butadiene copolymer and a specific monomer. Although this method has solved the above problems considerably, it is not yet complete.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a color liquid developer which has good color reproducibility and is suitable for electrostatic superimposition of a color superposition developing type without color superposition fog.

[0011]

[Means for Solving the Problems] In order to achieve the above-mentioned objects, studies have been made in the past, but a composition in which the non-aqueous resin proposed in the above patent is dispersed in a petroleum-based aliphatic hydrocarbon is proposed. They have found that they can be solved by using them, and completed the present invention.

That is, the constitution of the present invention is a color liquid developer for electrostatic photography as described in the claims.

The reason why the problems of the prior art can be solved by using the above-mentioned non-aqueous resin as the component of the toner is considered as follows.

The effect of resin A and resin B on image quality can be explained as follows.

The toner obtained by using the resin A is excellent in rechargeability, so that color superimposition is sufficiently performed and an image without color unevenness can be obtained, but it has a drawback that there are many color superposition fogs. The color reproducibility of primary colors such as black, cyan, and magenta is insufficient.

On the other hand, the resin B is so excellent that almost no color overlapping fog can be perceived, but the recharging property is slightly inferior to that of the resin A. Further, the resin B has a characteristic that it is excellent in dispersion stability.

In the present invention, by using the toner obtained by specifying the ratio of the resin A and the resin B, sufficient color superimposition can be obtained because of excellent rechargeability, and color superimposition due to residual potential is obtained. Since fogging hardly occurred, a color image with good color reproducibility was obtained. When the resin A is polymerized, an aromatic solvent having good solubility is used, and the solvent is further replaced with a petroleum aliphatic hydrocarbon solvent having a low dielectric constant before compounding the toner. The effect of (1) was improved, and the decrease in image density due to charge leakage was suppressed.

To produce the resin A dispersed in the petroleum-based aliphatic hydrocarbon of the present invention, at least one of a styrene-butadiene copolymer and a vinyltoluene-butadiene copolymer is dissolved in an aromatic solvent. Then, at least one kind of monomer selected from the general formula I is added dropwise, and the presence of a polymerization initiator such as azobisisobutyronitrile (AIBN) and benzoyl peroxide (BPO) which initiates the polymerization at a relatively low temperature. The polymerization reaction is carried out at a temperature of about 60 to 120 ° C. for 3 to 20 hours. Polymerization rate of 90% or more,
Preferably, when 95% or more is reached, a petroleum-based aliphatic hydrocarbon having a boiling point higher than that of the aromatic solvent is added and heated under normal pressure or reduced pressure, and the aromatic solvent is distilled off.

In the above polymerization reaction, the weight ratio of the copolymer to the monomer of general formula I is 30 to 90/10 to 70.
The amount is appropriate, and the amount of the polymerization initiator is preferably about 0.1 to 5% (weight) of the amount of the monomer.

On the other hand, in order to produce the resin B, the monomer of the general formula I and at least one kind of monomer selected from the group of monomers insoluble in the solvent when homopolymerized in a petroleum-based aliphatic hydrocarbon are used. 60 to 60 in the presence of a polymerization initiator such as AIBN or BPO in a petroleum-based aliphatic hydrocarbon.
The polymerization reaction may be carried out at a temperature of about 120 ° C. for 3 to 20 hours.

Specific examples of the above aromatic solvent include benzene, toluene, xylene, etc., with toluene being preferred. Specific examples of petroleum-based aliphatic hydrocarbons are n-octane, isooctane, decane, isododecane, isononane, and commercially available products are Isopar G, H, L and K manufactured by Exxon; Naphtha No. 6 and Shell manufactured by Shell Oil Co. There are sols. Isopar is preferred.

The monomer represented by the general formula I is a monomer which can be a solvated component even after polymerization, and specific examples thereof include lauryl methacrylate, lauryl acrylate, stearyl methacrylate, stearyl acrylate, 2-ethylhexyl methacrylate and 2-ethylhexyl acrylate. , Dodecyl methacrylate, dodecyl acrylate, hexyl methacrylate, hexyl acrylate, octyl methacrylate, octyl acrylate, cetyl methacrylate, cetyl acrylate,
Examples include vinyl laurate, vinyl stearate, nonyl methacrylate, nonyl acrylate, decyl methacrylate, decyl acrylate, cyclohexyl methacrylate, cyclohexyl acrylate.

Specific examples of the monomer which becomes insoluble in the non-aqueous solvent when homopolymerized are acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, methyl methacrylate, methyl acrylate and ethyl methacrylate. , Ethyl acrylate, propyl methacrylate, propyl acrylate, n-butyl methacrylate, isobutyl methacrylate, vinyl acetate, vinyltoluene, styrene, dimethylaminoethyl methacrylate, hydroxyethyl methacrylate,
Examples thereof include acrylonitrile, vinylpyrrolidone, vinylpyridine and the like. Examples of the polymerization initiator used in the present invention include phenylazotriphenylmethane, lauroyl peroxide, t-butyl peroxide and the like in addition to the above AIBN and BPO.

Here, some production examples of the resin A and the resin B will be described.

Resin A, Production Example (1) 3.0 equipped with stirrer, thermometer, cooling tube and dropping funnel
To a liter flask, 400 g of toluene and 300 g of styrene-butadiene resin (Pryolite S-5, manufactured by Goodyear Co., Ltd.) were charged, and while being heated to 80 ° C., a monomer solution consisting of 400 g of 2-ethylhexyl methacrylate and 10 g of benzoyl peroxide. Was added dropwise over 2 hours. After that, polymerization was carried out at this temperature for 7 hours. As a result, a resin dispersion having a polymerization rate of 96.5% was obtained. Next, 400 g of Isopar H was added, and a distillation apparatus was provided, and toluene was distilled by gradually heating at normal pressure. Inner temperature 148 ° C
When heated up to 480 g, a distillate of 480 g was obtained. The gas chromatographic analysis value was 84.5% of toluene. 80 g of Isopar H was added to obtain a resin dispersion.

Resin A, Production Example (2) To the same flask as in Production Example (1), 400 g of toluene and 300 g of vinyltoluene-butadiene resin (Pryolite VT, manufactured by Goodyear) were charged, and the mixture was heated to 90 ° C. while stirring. Lauroyl methacrylate 400 in
and a monomer solution containing 10 g of lauroyl peroxide were added dropwise over 2 hours. Then, polymerization was carried out at this temperature for 8 hours. As a result, a resin dispersion having a polymerization rate of 95.5% was obtained. Next, add Isopar H, install a distillation device,
Toluene was distilled by heating gradually under reduced pressure. Decompression degree 10
When heated to an internal temperature of 70 ° C at 0 mmHg, 520 g
The distillate was obtained. Gas chromatographic analysis value is toluene 77.
It was 5%. 120 g of Isopar H was added to obtain a resin dispersion.

Resin B, Production Example (1) 2.0 equipped with stirrer, thermometer, cooling tube and dropping funnel
Charge 750g of Isopar H into a 1 liter flask,
While heating to 80 ° C., a monomer solution consisting of 400 g of 2-ethylhexyl methacrylate, 200 g of styrene, 150 g of n-butyl methacrylate and 10 g of benzoyl peroxide was replaced with nitrogen while being replaced with 3
Dropped over time. Then, polymerization was carried out at this temperature for 12 hours. As a result, a resin dispersion having a polymerization rate of 95.2% was obtained.

Resin B, Production Example (2) 2.0 equipped with stirrer, thermometer, cooling tube and dropping funnel
Charge 750g of Isopar H into a 1 liter flask,
While heating at 80 ° C., a monomer solution containing 500 g of lauryl methacrylate, 250 g of styrene and 10 g of benzoyl peroxide was added dropwise thereto over 3 hours while purging with nitrogen. Then, polymerization was carried out at this temperature for 14 hours. As a result, a resin dispersion having a polymerization rate of 96.2% was obtained.

In order to obtain a color liquid developer for electrostatic photography using the resin thus obtained, 1 part by weight of the resin A and / or resin B of the present invention is added to 1 part by weight of the colorant.
5 to 5 parts by weight (as resin solids) and 10 to 30 parts by weight of carrier liquid are kneaded and dispersed in an attritor, a ball mill, a sand mill or the like to obtain a concentrated toner, which may be diluted with a similar carrier liquid if necessary. Good.

A charge control agent such as a fatty acid metal salt may be added, if necessary, during or after the preparation of the concentrated toner.

As the colorant, general inorganic / organic pigments can be used, but the following ones are more preferable as the color developer type liquid developer for electrostatic photography.

<Black> Carbon black (furnace black, channel black, acetylene black, etc.) <Cyan> phthalocyanine blue (β type) <Magenta> naphthol AS-based insoluble monoazo pigment <yellow> acetoacetic acid arylamide-based insoluble disazo pigment As the carrier liquid used for the liquid developer, the petroleum-based aliphatic hydrocarbon or its derivative is preferable.

Specific examples thereof include paraffinic or isoparaffinic hydrocarbons (such as Isopar H, Isopar G, Isopar L, and Isopar K manufactured by Esso Co.), ligroin, n-hexane, isooctane, cyclohexane, etc. alone or Two or more kinds are used in combination.

[0034]

The present invention will be specifically described with reference to the following examples. The amounts (parts) of each component described in the examples are parts by weight.

Example 1 <Cyan> Phthalocyanine blue 5 parts Resin A Production Example 1 (solid content conversion) 8.5 parts Resin B Production Example 2 (solid content conversion) 1.5 parts Isopar H (including solvent in resin) ) 85 parts <Magenta> Naphthol carmine 5 parts Resin A Production Example 1 (solid content conversion) 8.5 parts Resin B Production Example 2 (solid content conversion) 1.5 parts Isopar H (including solvent in resin) 85 parts <Yellow> Disazo Yellow AAA 5 parts Resin A Production Example 1 (as solid content) 10 parts Isopar H (including solvent in resin) 85 parts <Black> Carbon black 5 parts Nigrosine 2 parts Resin A Production Example 1 (solid content) 8.5 parts Resin B Production Example 2 (solid content conversion) 1.5 parts Zirconium naphthenate (metal content 4%) 0.25 parts Isopar H (including solvent in resin) 82.75 parts Mixture as a concentrated toner each 24 hours dispersed with a ball mill of, was diluted to prepare a set electrostatographic color liquid developer in Isopar in 1 liter thereof 50 g. Then, this is electrostatic color plotter CE-343.
6 (manufactured by Versattec Co., Ltd.) was repeatedly subjected to latent image formation and development in the order of black, cyan, magenta, and yellow, and a color image excellent in color reproducibility with almost no color overlapping fog was obtained.

Example 2 A set of liquid developers was prepared in exactly the same manner except that the resin A and the resin B of Example 1 were replaced by the resins of Production Example 2.

When a color image was printed in the same manner as in Example 1, almost no color overlapping fog was observed and the secondary color reproducibility was good.

Comparative Example 1 For each of the cyan, magenta, and black toners of Example 1, one set of liquid developer was prepared in exactly the same manner except that the resin composition of the toluene dispersion solution was used as the resin A.

When a color image was printed in the same manner as in Example 1, other toner adhered to the black, cyan and magenta images, and there were many color overlapping fogs.

Table 1 shows the image quality of Examples and Comparative Examples.

[0041]

[Table 1]

Evaluation method 1. Image density Macbeth reflection density system RD-914 2. Color overlay fog The color difference in the CIE-1976 Lab * color system and the change in color before and after color overlay were measured with a color difference meter. An ideal value for color fog is zero color difference. 3. Secondary reproducibility Color difference of 10 or less with RGB as a reference color of offset process printing is ○, and 10 or more is ×.

[0043]

As is apparent from the comparison between the examples and the comparative examples, the color liquid developer for electrophotography having the constitution of the present invention has almost no color overlapping fog and good reproducibility of secondary colors. When it is used for color superposition type electrostatic photography or electrostatic recording, it has a remarkable effect on color reproducibility and color discrimination.

Front page continuation (72) Inventor Nobutaka Kinoshita 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (3)

[Claims] 1. A color liquid developer for electrostatic photography in which a carrier liquid contains a toner mainly composed of a pigment and a resin, wherein the resin is the following resin A and / or resin B. A color liquid developer for electrostatic photography. Resin A A styrene / butadiene copolymer and / or vinyltoluene / butadiene copolymer obtained by polymerizing a monomer represented by the following general formula I, which is dispersed in a petroleum-based aliphatic hydrocarbon. Aqueous Resin, Resin B A non-aqueous resin obtained by polymerizing a monomer represented by the following general formula I and a monomer which becomes insoluble in the solvent when homopolymerized in a petroleum-based aliphatic hydrocarbon solvent, the general formula I Here, R is H or CH ₃ X is an -COOC _n H _{2n + 1} or -OCOC _n H _{2n + 1,} n in these substituents 6-20 integer. 2. The resin A is produced by completing the polymerization reaction in an aromatic solvent, adding a petroleum aliphatic hydrocarbon, and then removing the aromatic solvent. The color liquid developer for electrostatic photography according to claim 1. 3. The weight ratio of the copolymer in the resin A to the monomer represented by the general formula I is 30 to 90/10 to 70.
The color liquid developer for electrostatic photography according to claim 1, wherein